Tech Briefs Magazine - August 2024 - 25

Pierre Levesque from Montreal had
shown that trace amounts of oxygen can
slow the growth process and even etch
the graphene away. So, about six years
ago, Christopher DiMarco designed
and built a CVD growth system in which
the amount of oxygen introduced
during the deposition process could be
carefully controlled.
Current Ph.D. students Xingzhou Yan
and Jacob Amontree continued DiMarco's
work and further improved the
growth system. They found that when
trace oxygen was eliminated, CVD
growth was much faster - and gave the
same results every time. They also studied
the kinetics of oxygen-free CVD
graphene growth and found that a simple
model could predict growth rate
over a range of different parameters, including
gas pressure and temperature.
The quality of the OF-CVD-grown
samples proved virtually identical to
that of exfoliated graphene. In collaboration
with colleagues in Columbia's
physics department, their graphene displayed
striking evidence for the fractional
quantum Hall effect under magnetic
fields, a quantum phenomenon
that had previously only been observed
in ultrahigh-quality, two-dimensional
electrical systems.
From here, the team plans to develop
a method to cleanly transfer their
high-quality graphene from the metal
growth catalyst to other functional substrates
such as silicon - the final piece
of the puzzle to take full advantage of
this wonder material.
For more information, contact Holly
Evarts at he2181@columbia.edu; 212854-3206.
New
Methods in Preparing and Purifying Nanomaterials
New processes greatly improve the properties of boron nitride nanomaterials.
Glenn Research Center, Cleveland, OH
I
nnovators at NASA's Glenn Research
Center have made several breakthroughs
in treating hexagonal boron nitride
(hBN) nanomaterials, improving their
properties to supplant carbon nanotubes
in many applications. These inventors
have greatly enhanced the processes of
intercalation and exfoliation. Both processes
are crucial in creating usable nanomaterials
and tailoring them for specific
engineered applications.
In addition, Glenn's researchers have
devised a means of fabricating exfoliated
hBN-alumina ceramic composites, which
have great potential as high-thermal-conductivity
electrical insulators, as well as a
new method to remove impurities from
nanomaterials without causing damage
to their structures.
Sometimes called white graphite, affordable
and plentiful hBN possesses the same
kind of layered molecular structure as
graphite. In graphite, this structure has allowed
next-generation nanomaterials like
carbon nanotubes and graphene to be produced.
With hBN, however, the process of
converting the substance into boron nitride
nanotubes (BNNT) has been too difficult
to yield commercial quantities.
Glenn innovators have created several
new methods that could enable greater
adoption of this unique nanomaterial.
In the initial stage, the starter reactant is
mixed with a selected set of chemicals (a
metal chloride, for example) and an activation
agent (such as sodium fluoride).
This mixture causes hBN to become less
resistant to intercalation. The intercalated
product can then be exfoliated by
heating the material in air and giving the
Tech Briefs, August 2024
Glenn's novel and effective process for fabricating
hBN nanomaterials opens new territory
for a variety of applications, including microelectronics.
(Image: NASA)
material a final rinse with a liquid-phase
ferric chloride salt to dissolve any embedded
impurities without damaging its
internal structure.
These efficiently exfoliated nanomaterials
can be used to form advanced composite
materials (e.g., layered with aluminum
oxide to form hBN/alumina
ceramic composites). Nanomaterials fabricated
from hBN can also take advantage
of the material's unique combination of
being an electrical insulator with high
thermal conductivity for applications
ranging from microelectronics to energy
harvesting. Glenn's innovations have enabled
a significantly improved matrix
composite material with the potential to
www.techbriefs.com
Glenn's hBN nanomaterials excel as electrical
insulators and thermal conductors, an invaluable
combination for energy-harvesting applications.
(Image: NASA)
make a significant impact on the commercial
materials market.
All these advances have hBN nanomaterials
set to transform applications such as
heat sinks, electrical insulators, lightweight
piezoelectric polymers for satellites and unmanned
aerial vehicles, ceramic composites
for jet engines, biomedical components,
and radiation shielding technology.
NASA is actively seeking licensees to
commercialize this technology. Please
contact NASA's Licensing Concierge at
Agency-Patent-Licensing@mail.nasa.gov
or call at 202-358-7432 to initiate licensing
discussions. For more information, visit
https://technology.nasa.gov/patent/
LEW-TOPS-107.
25
https://technology.nasa.gov/patent/LEW-TOPS-107 https://www.techbriefs.com
Tech Briefs Magazine - August 2024

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